Recently, various optical instruments have come to be used to observe the ocular fundus as an inspection object. For example, an anterior segment imaging device, fundus camera, confocal scanning laser ophthalmoscope, and optical coherence tomographic imaging apparatus (low-coherence, optical coherence tomographic imaging apparatus: hereinafter referred to as an OCT apparatus) are used.
Among others, the OCT apparatus, which allows tomographic images of the ocular fundus to be obtained at high resolution, is currently becoming an indispensable apparatus for specialized retinal outpatient clinics. Also, the OCT apparatus is finding applications in other areas such as the endoscopy area and drawing attention as an apparatus used to obtain arbitrary tomographic images.
The OCT apparatus irradiates the retina with low coherence light, causes scattered light and reflected light, i.e., returning light of the low coherence light, to interfere with reference light and thereby images a layer structure of the retina at high sensitivity. By scanning an inspection object with the low coherence light, the OCT apparatus can obtain tomographic images. In particular, tomographic images of the retina are widely used for ophthalmologic diagnosis.
The OCT apparatus, which is used for diagnosis such as described above, is required to obtain a wide range of tomographic images or high-resolution tomographic images.
Also, to reduce the burden on patients, there is demand to reduce measurement time.
To achieve a reduction in the measurement time, U.S. patent application publication No. 2008/0284981 discloses a multi-beam OCT apparatus which uses a Michelson interferometer for irradiating the retina with multiple beams.
Also, an OCT apparatus for detecting attendant movement of the eyeball is disclosed by M. Pircher et al. (Michael Pircher, Bernhard Baumnn, Erich Gotzinger, Harald Sattmann and Chirstoph K. Hizenberger, “Simultaneous SLO/OCT imaging of the human retina with axial eye motion correction,” Optics Express, 10 Dec. 2007, Vol. 15 No. 25 16922-16932).
The reason why such detection is carried out is that the OCT apparatus, which constructs images by scanning, takes relatively much time for imaging and that obtained images are affected by movement of the human eyeball (involuntary eyeball motion known as flicks, i.e., anteroposterior motion of the eyeball together with the entire head).
A technique according to “Simultaneous SLO/OCT imaging of the human retina with axial eye motion correction,” Optics Express, 10 Dec. 2007, Vol. 15 No. 25 16922-16932 described above detects anteroposterior corneal position using a low coherence interferometer.
The technique determines amounts of anteroposterior eyeball movement based on detected values of the anteroposterior position, corrects the optical path length of reference light of the low-coherence, optical coherence tomographic imaging apparatus for the amounts of eyeball movement, and thereby reduces anteroposterior deformation of the eyeball in images obtained by the low-coherence, optical coherence tomographic imaging apparatus.